1. Field of the Invention
This invention relates to an air conditioner which supplies air at a controlled specified temperature and humidity to a coating booth.
Generally the finishing quality of a coating or paint in a coating booth highly depends upon the temperature and humidity of the air led in the coating booth. Therefore, especially in case of, for example, a body of an automobile or the like, which is required to have a high quality coating, not only must the air supplied to the coating booth have dust eliminated therefrom, but also the temperature and the humidity of the air are strictly controlled to specific limits.
Accordingly, this invention relates to an improvement in the air conditioner for the coating booth to be used in coating an automobile body or the like which is required to have a high quality coating.
2. Description of the Prior Art
In the conventional air conditioner for controlling the air supplied to the coating booth at a predetermined temperature and humidity, dust in the air is first eliminated by a filter. The clean air is then passed between plate fin coils in which heated steam flows, to transmit heat to the air. Subsequently the air thus heated goes by articles, called "wet wall units" on the surface of which heated water flows down from the top to the bottom of the articles. The air is humidified due to the contact of the air with the heated downward flowing water. Subsequently the air is again heated by passing through another plate fin coil heater within which flows steam.
In order to humidify the air to a predetermined humidity in this humidifying step of the conventional air conditioner, it is necessary to heat the water which flows down the so-called wet walls to some predetermined temperature. Normally, the heated water thus flowing down the surface of the wet walls is supplied as recirculating water for energy-saving reasons. Thus, a predetermined amount of the energy for heating the recirculating water is used to humidify the air passing by. In this case, the smaller the ratio of the recirculating water to the amount of air which passes by the wet walls, the higher the temperature of the recirculating water should be. However, since the recirculating water is normally preheated in a tank where the water is stored after flowing down on the wet walls, there occurs a temperature difference for the heated water between the upper portion of the wet walls from which the recirculating water starts flowing and the lowermost portion of the wet walls. This temperature difference can become large, so that to ensure the humidification of the air even at the lowermost portion of the wet walls, the initial temperature of the recirculating water must be so high that the air which passes through the upper portion of the wet walls is excessively humidified and becomes supersaturated. Thus, foglike water droplets are produced in the air, and the temperature and humidity of the air cannot be sufficiently controlled. Further, water droplets can precipitate in a duct leading to the coating booth. Therefore, a large amount of recirculating water must normally be provided for reducing and equalizing the temperature difference between the upper portion and the lowermost portion of the wet walls. Accordingly, a large amount of energy is wasted.